


A Weekend Rut

by Arixese



Series: Tumblr Requests [3]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Anal, Biting, Breeding Kink, Cunnilingus, Dirty Talk, Double Penetration, Double Penetration in Two Holes, F/M, Female Reader, M/M, Monster Heat, Multi, Multiple Orgasms, Threesome - F/M/M, Underswap Papyrus, Underswap Sans, aphrodesiac
Language: English
Status: In-Progress
Published: 2017-07-06
Updated: 2017-07-06
Packaged: 2018-11-28 11:44:14
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,191
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11417262
Author URL: https://archiveofourown.org/users/Arixese/pseuds/Arixese
Summary: It’s Saturday. The first day of your weekend after a rough workweek, but, apparently, you are not allowed to sleep in. Something is urgent, and him and Papy both need you. He won’t say why, but they both need you. So, you come by to check on them and… Why’s it so hot? And, oh, God, that smell…Requested by prettyincubone on Tumblr, who asked for threesome, monster heat, dirty talk, and breeding kink Featuring the Underswap bros





	A Weekend Rut

“You made it!”

The door swung open before you even made it on the front step, and you staggered back as Sans slammed into you, his arms ensnaring your waist in a hug. “Where have you been, Sugar? I called you  _ hours _ ago,” he cried out theatrically as he pulled you inside by the wrist, leading you into the living room. 

“Hey, cut me some slack; you’re the one that asked me to pack an overnight bag at the last minute, remember?” You adjusted the large satchel hanging off of your shoulder to give one of your beloved boyfriends a tight and proper hug. You were surprised to feel him shift uncomfortably in your arms when you brought him in closer, and even more surprised when he broke away,a pale blue sheen covering his skull. “Are you okay, there, lover? You’re not looking too hot.”

“W-What’re you talking about?! The Magnificent Sans is the epitome of hot!” Sans struck a pose with a loud guffaw, his posture quickly slacking as he caught the skeptical glance you were throwing at him. “Mweheheh, um…” 

“Well, of course you are, but…” You felt your forehead scrunch up in worry at Sans’s unusual behavior. It wasn’t like him to look so self-conscious. “So, uh, anyway, what’s-… Whoa…” You dropped your bag at your feet as you suddenly became aware of an oppressive, humid air sticking to your skin…. It was almost unbearably hot as it rolled off of you in waves… but, it also smelled so alluring; almost sweet, yet it also smelled strongly of musk and sweat. You sucked your bottom lip between your teeth; everything smelled so good, and it was so strong you could basically taste it in the air. You sniffed in confusion as you felt it radiating off of the walls, and your skin tingled. You rubbed your thighs together uncomfortably, your mind buzzing and fuzzing over the longer you thought about it. You stumbled back and felt Sans’s hands on your waist, catching you before you fell. You pressed a hand to your forehead as you tried to regain your sense of balance. It was only then that you noticed Sans’s hands lingering on your back, rubbing gently along your hips as he whined low in the back of his throat. “Sans…?”

“Sans? What’s going on, out there?” You looked up and saw Papyrus’s bedroom door open. 

“Uh, hi, Honey, I’m home,” You joked feebly with a small smile, suppressing the cold shock running through your system when you caught his grave expression. Papyrus looked absolutely  _ livid _ , his eyes narrowed and intense compared to his brother’s bored, half-lidded stare over your shoulder. You rolled yourself out of the shorter skeleton’s arms and looked between the two in confusion. The tension in the air was palpable, and your brain struggled to decide on an appropriate reaction. This… wasn’t jealousy or anything was it? You’ve all been in a happy, working, polyamorous relationship with each other for months. If anything, you were expecting Papyrus to make some joke about ‘starting the fun without him,’ or, if he was really horny, teleporting himself right into the action so they could both indulge, as he's done many a time. Either way, whether one-on-one or as a group, neither brother seemed to mind sharing you, before... You had always figured that jealousy between the two of them was a thing that just did not happen… Did it? You hesitated before addressing it in a roundabout manner. “Is… something going on?”

Sans stepped back away from you and faced the taller skeleton as he shifted restlessly on his feet. “Alright, Papy, just hear me out-,”

Papyrus interrupted with a low growl. “Sans, I thought we agreed not to bring her into this?” You blinked in surprise. So, that makes, what,  _ you _ the problem? Why? Your brow furrowed as you tried making sense of the situation. But, all you could really latch onto was that peculiar aura that still permeated the room, amplifying the tension and making your head cloudier as you let yourself become distracted. Like Sans, you noticed a bright orange flush marring Papyrus’s cheekbones, his hoodie discarded to reveal his bones glistening with sweat. You licked your lips as you stared at the way his black tank just hung off his clavicles. You bet he tasted delicious right now…

Ugh, no, stop stop stop. You resisted the urge to slap yourself harshly to bring yourself back to reality. Sans spoke up passionately as he yelled over your quiet questions. “I don't think we have any choice, anymore, brother,” he yelled, “I mean, stars, Papyrus, ‘taking care of it ourselves’ just isn’t working, anymore! If anything, that’s only making it  worse the longer we hold out!”

“Jesus fucking  _ Christ _ , you two,” you shrieked in exasperation. Would someone kindly explain what in the actual hell’s going on with you guys!?”

“Language,” Sans reminded impulsively, which you chose to ignore.

“Cause this,” you waved your hand around wildly as you indicated the fluctuating wave of sex pouring in from every corner of the room. You obviously couldn't be the only one feeling that. “Combined with your dumb bickering, is driving me nuts!”

“You mean… Sans didn’t tell you  _ anything _ about what's happening, right now?” Papyrus groaned in frustration when you shook your head. He looked over your shoulder at Sans and pinched his temple between his fingers with an exaggerated sigh. “You could have at least explained before inviting her over, Bro… You know, make this less awkward than it has to be?” 

“I was gonna, really… she just smelled so good…” 

Suddenly, it clicked for you. The smell, the overwhelming tension and sensitivity in the air… You shifted your weight awkwardly as you tried to phrase your question properly. “Hey, guys, be straight with me, here…Are you both in heat, right now?” Both brothers blanched and looked away guiltily before nodding. “Why didn’t either of you tell me, sooner?”

“Papyrus thought we could handle it on our own,” Sans mumbled as he scratched the back of his skull awkwardly.  “And we did. For a while, at least. Then, just mastubating stopped working after a while.”

Your mind glazed over with the sudden mental image of the brothers each in their own beds, moaning and writhing around as they jerked themselves off desperately. Oh, you could almost hear them both whimpering your name… You wondered if they ever came with you on their minds. Wait, no. Fuck. Stop that. As sexy as that image was, you furrowed your brow deeply as you realized the obvious gap in logic. “Wait, why  _ not _ call me, then? It’s not like sex has ever been out of the question, before…” 

“You don’t understand. If…” Papyrus hesitated before continuing. “If you decide to stay here, neither of us’ll be able to control ourselves. I mean, once we get started, we simply won't  _ want _ to. And you do know what happens to monster magic during our heats, right?”

It was your turn to nod. “Yeah, that means it’s going to be easier for you guys to breed. Who said I had a problem with that? You’d both make excellent fathers if you wanted to be..” Sans and Papyrus’s souls both stuttered at the proclamation. “I mean,” you rambled, “I would have preferred it if you both came out and asked for my help  instead of putting yourselves through hell... Looking at you, Papyrus.” Papyrus hunched over in embarrassment as you shot him a look. “But, yes, definitely. I have no problems bearing your children, whether that happens now or later…” You paused as a thought suddenly occurred to you.  “...Unless it’s because you guys just don’t want kids in the first place? Is that why you didn’t want me to stop by?” 

“No, no, no!” “God, no! It’s not that at  _ all _ !”

You blinked in surprise at the intense and instantaneous reaction. Papyrus cleared his throat awkwardly. “What we’re trying to say is:Yes we want kids. With you. Fuck, Sans and I talk about it all the time! It’d be amazing! Just seeing you waddling around, glowing, carrying  _ our _ offspring and bringing it into the world like a goddamn miracle… I mean, god, that sounds like the sexiest thing ever!” Sans surprised you as he nodded along eagerly, not bothering to say anything about his brother’s language. You absentmindedly rubbed your thighs together, pausing to collect your thoughts as it steadily got harder and harder to concentrate on anything but the wave of skeleton pheromones washing over you and the wet, bubbling heat rising between your legs. 

“I had no idea,” you mumbled.

“And we had no idea how to even bring it up, so I guess we're even, huh?”

“We could have just asked if you weren’t such a baby bones about it…”

“Shut up, Sans.”

You laughed softly and reached out to cup both of their faces on your hands. “Guys, I shouldn’t have to remind either of you how much I love you. I’m the luckiest person in the world when I'm with you.” You groaned inwardly at how cheesy that was, but the brothers didn't seem to mind as they gawked at you openly.

“ _ Jesus _ , Kitten, keep saying stuff like that, and we might not stop at just one…” You shuddered as Papyrus gripped the back of your head, his fingers tangling in your hair as he crashed his mouth against yours. You moaned loudly as Papyrus’s tongue forced its way past your teeth, assailing your taste buds with the sweet taste of raw honey and citrus. 

“Brother, come on, don’t take her all for yourself… Let me have some fun, too,” he whined as he ripped your shirt off your shoulders, his hands reaching into your bra as he groped and fondled your breasts. You moaned loudly and your nips hardened with arousal between his fingers. Your skin tingled with acute pleasure and sensitivity everywhere the skeletons touched you, the excess magic from their souls sharpening every receptor on your body. You reached blissfully into Papyrus's back pockets as the brothers rutted into you from either side, the three of you all sighing and grunting from the amazing friction. “Oh, gosh, Sugar, you’re  _ so _ soft,” Sans moaned as he pressed small kisses between your shoulder blades, holding you close as he dry humped against your backside and fondled your breasts in his hands.

“And so sweet too” Papyrus added with a small gasp of air as he broke away from your mouth to nibble at your shoulder. “Christ, Kitten, you taste so fucking  _ divine _ .” You bit your lip and groaned quietly as you shifted your weight from side to side, rubbing your thighs together as you felt your underwear begin to soak even further with arousal. Papyrus snickered as your hips pressed into his erection desperately. “Nyeh heh heh… Looks like  _ someone’s _ enjoying themselves,” he cooed softly. You yelped as Papyrus suddenly unlatched his mouth from your shoulder and flipped you over in his arms, your back settling against his sternum. “Sans, you want a taste? I’ve got it covered up top.” 

Sans wasted no time with the suggestion and tugged harshly at the waistband of your shorts, yanking them down past your knees. “Unf, Papy, you won’t  _ believe _ how wet she is,” Sans gushed loudly, earning a high pitched whine as he traced your slit through your panties with his thumb.You shivered as Sans pulled the crotch of your panties to the side, exposing you to his hot breath. “ _ Ohhh, Sugar, _ ” he moaned blissfully, “You smell good enough to  _ eat.” _

“Go ahead, bro; I think she likes it,” Papyrus teased as his thumbs pressed against your nips and toggled them around. “Oh-hoho, yeah, you’re really  _ perking _ her up from down there.” You giggled softly at the puns, the sound flowing steadily into a long, drawn-out moan as Sans slipped his tongue between your folds to lap at your clit, and you shifted your weight when he gently raised one of your knees off of the floor, tugging  your shorts and underwear all the way down your legs. Once he was done, he spread your thighs for a better angle before lapping again at your clit. You almost screamed when you felt a pair of forefingers slide into you, and you pressed your hips forward as Sans’s tongue and fingers worked in tandem. 

“Mmm, mind if I taste you some more, Kitten? Don’t want Sans to have all the fun…” Papyrus grasped your chin and pulled you to face him. He captured your mouth with ernest as your tongues intertwined once more, muffling the pants and moans threatening to spill from you as Sans worked you up and down, thrusting his fingers into you at a rapid pace. You huffed through your nose and whined loudly into Papyrus’s mouth, reaching up to pull him closer into you as your hips shook in San’s hands. A white hot pressure built up between your legs quickly in a flash before exploding on Sans’s tongue as he caressed your outer thighs, drinking your orgasm greedily while your hips shuddered and spasmed. 

“I’ll never get tired of that taste,” Sans moaned as he rose to his feet, his hand rubbing at the erection straining against his crotch. “So delicious.”

“You okay, Sweetness?”

“Uh huh…” You nodded your head weakly as you stared vacantly at the ceiling and recovered from your orgasm. 

“Sans, what do you say we take this upstairs, hm? Make things more comfortable for our  _ sweet _ lil’ kitten?” You moaned in Papyrus's arms as he bit down gently on your shoulder, and Sans stared a moment as their boners strained desperately against their pants.

“As long as we use my room,” Sans said as he tried to hide his excited smile behind a serious, chiding expression. “No child of mine is gonna be conceived in that filthy disaster you call a bed!” You giggled absently as you wrapped your arms around Papyrus’s shoulders, allowing him to pick you up and teleport you to the bedroom. Oh yeah, you almost forgot about that: both of them want kids… Holy shit. You were going to be a mom when everything’s said and done, weren’t you? 

Sans was already undressed when you opened your eyes, his girthy blue cock greeting you at attention as he stood at the side of the bed, stroking himself as he stared hungrily at you. Your mouth watered at the vibrant, pulsing blue, precum dribbling uncontrollably from the tip, his body shuddering as he swiped his thumb along the slit before coating himself in it, and his cock glistened from the lubrication. You yelped as a hand swatted against your ass without warning. “Don’t keep him waiting, ‘Sugar,’” Papyrus whispered huskily in your ear, and your body shuddered at the way Sans’s personal nickname lifted off of his brother’s tongue. 

“Are you gonna join us, Honey?,” you asked expectantly as Sans reached out and guided you over to the bedside, letting go only briefly to lower himself down onto the mattress before letting you climb on his lap. The taller skeleton hummed in affirmation as he tossed his black tank to the side, one hand stroking his spine as the other rubbed through his khakis to stimulate his pelvis. 

Sans let out a breathy moan as he grasped your chin roughly and turned you away from his brother. “He’ll be here in a minute,” he growled as he reached up to capture your mouth in his, and Sans groaned in your mouth when you eased your hips down to grind over his slick shaft. You both coated each other with arousal as you savored the exploding flavor of his mouth, letting it mingle with the traces of Papyrus’s on your tongue. Sans's fingers racked on you skin and smothered your moans as you arched your back into it, your hips curling to press yourself deeper along his shaft. “Ah, I feel you twitching,” Sans huffed as he broke your kiss, his hands reaching down to grab the swell of your ass as his fingers sank into your flesh. “Does that mean your tight little pussy is ready for my cock?” You spasmed at Sans's sudden language and your face glowed bright red as your arms wrapped behind Sans's neck to bury your face in him. 

“Heh, I think it does, Bro,” Papyrus wheezed in pleasure behind you both above the vague clicking and slapping of his hand fiercely tugging at his cock and spine, and you felt Sans's cock twitch in response. Sans growled as he yanked your hips further up his cock, and your throat gurgled out a scream as he slammed you down. Your arms tightened behind his neck for dear life as you felt your downstairs explode in a shower of fleeting pain as you struggled to accommodate his girth. Sans's hands pushed firm on the tops of your thighs to keep himself sheathed in you, his eyes fuzzing and rolling around in his skull as he felt you contract and loosen wildly around him.

“Stars, you feel so tight,” he groaned as you wiggled your hips slightly to get a good feel for him. Was it just you, or did he get bigger? You doubted you were really so tight after cumming so hard, earlier. Sans apparently took your wiggling as an invitation as his hands switched to the back of your thighs and pulled you up his dick before thrusting eagerly and pulling you back down. You moaned and huffed forcefully through your nose as you bit your lip to hold back from screaming as Sans's dick pounded into you. As exquisite as his cock felt, you were very much aware of the other naked skeleton standing in the corner. If you knew Papyrus at all, which you believed you did, then you knew he’d give you something to  _ really  _ scream about. Unfortunately, Sans seemed to disagree with that notion, and you yelped as you felt something yank against your hair, pulling your head back and exposing your throat. Your jaw fell slack and your eyes wrenched shut as a shrill whine escaped your throat. “Much better,” Sans mumbled smugly, and you groaned loudly as you felt him nibble on your exposed neck. “I like it when you sing for me, Sugar; let me hear more.” Your eyes flew open with a gasp as Sans pressed down on your ass and drove his cock even deeper into you before pulling you up and slamming you back down on harsh repeat.. 

“Oh…  _ Ohhh, fuck _ . Fuck!! Sans!” Your hands dove under him to clutch the back of his ribs as you met his thrusts, eagerly. Sans’s teeth latched harshly against your shoulder and blood dribbled from the wound as your walls clenched around him in warning. Sans growled into your shoulder and your hips quaked as they bounced on his dick. The rough, dirty talk only encouraged you as you slammed your hips against him, moaning and gasping for air. Your second orgasm came without warning, and your body jerked and twitched as cum spattered on Sans’s pelvis. You shuddered when you felt Sans's cock twitch inside of you, harder than ever. Your eyes flickered open as your senses became rapidly exhausted and hyper-aware. Oh, fuck, has he seriously not cum, yet?

“Ohhh… Stars…” Sans’s head fell back on his pillow as he stared blankly at the ceiling. It occurred to you after the fact that he could have very well been seeing  _ actual _ stars, a thought that later would make you giggle like a schoolgirl whenever you thought of it. 

“Geez, Sans, you’ running her ragged. Don't tell me you forgot to share?” You yipped in surprise when you suddenly felt Papyrus's hands on you, his palms stroking small circles on your hips.

“You took too long,” Sans huffed, and you whined as his fingers dug in your ass, the noise transitioning seamlessly into a rough scream as Papyrus's hand forced you back down. You and Sans both writhed on the mattress as you were stuffed to the brim with massive, magic cock, his head pressing so intensely into you that your heart hammered with fear of breaking. You looked over your shoulder to rant at the offending skeleton. But, what you saw made your jaw drop wordlessly.

“Yeah, well…” Papyrus’s tongue swiped along his teeth as he stared at your backside, his eye alight with golden fire as he caressed your hips in one hand while pressing firmly with the other. “I think our sweet little kitten is ready for one more, after all that cumming,” he drawled as he held you against Sans's pelvis and you jittered with excitement as you felt the flat end of his cock stroke against your ass. Sans whined under you as you arched your back and presented yourself earnestly. Papyrus's eyes drooped with arousal at the sight. “Damn, look how hungry you are, Kitten; needing two cocks to satisfy you.” You weren't sure who the comment affected more: you or Sans. But, both of you shivered at the implications, and the way Papyrus's voice rumbled in your ears like faraway thunder. Some more cum squirted out of you when he released the hand keeping you mashed against Sans’s pelvis, and you both sighed in relief. You felt Papyrus stroke the thick and viscous cum leaking around his brother's cock and start to coat your ass in it, stretching the hole gently with his fingers. “What do you say, Sweetness? Up for another go?” You shivered as he traced his slick fingers across your throat and nibbled on your ear.

Sans yelped before slamming a hand to his forehead and letting out a hoarse, exhausted laugh. “W-wowie… To think I was worried about your stamina! Mweh heh heh, that was  _ so _ tight!” 

“Yeah? Now, I’m curious.” Papyrus withdrew his fingers and straightened his back, taking his cock in his hand. “Let’s see…” You moaned as he pressed his cock against the hole, your muscles already relaxed from two orgasms. “Just how much you can  _ take _ !” The three of you screamed in pleasure as Papyrus breached you, and you all stopped moving as you took a moment to adjust. Your walls fluttered experimentally around them both as you clung to Sans’s frame, your breath hot and labored on the base of his neck. It felt so full… You groaned as Papyrus moved first, shifting his hips slowly while Sans followed immediately after. The rhythm was rocky, at best, and completely out of sync, and you grunted loudly as you started moving on your own to dictate the pace. Papyrus growled with satisfaction and nipped at your shoulder, staying far away from the angry red marks Sans left behind. Papyrus bent over both of you, grabbing your breast in his hand as he propped himself up by Sans’s shoulder, making you gasp and shudder as his cock dove into you at a deeper angle.  You cried out between thrusts, your head tossed back against Papyrus’s shoulder, your fingers tensing from the sheer force building and building as both brothers slammed into you in tandem. A jolt of pleasure zapped through your body and you screeched as one of them brushed over a bundle of nerves deep inside of you. Your eyes saw nothing but cloudy white. Someone was close; you felt someone’s cock jerk violently every time they both pulled out, and you screamed for someone to cum.

It wasn’t until you collapsed with a shudder that you realized who’s cum shot up into you before splattering on their dick. Sans whined under you, begging you to roll off as both skeletons withdrew from inside of you. “You okay there, bro?,” Papyrus asked nonchalantly, his arm clinging around your waist, feeling your body spasm under him as his thumb drew circles around your bellybutton. Sans gasped and swallowed desperately, holding up his hand as he doubled over his knees.

“I’ll… Be right back,” Sans choked as he staggered out the bedroom door. “I just…  _ Hoo _ … I need to drink some water or something.” Your breath wheezed and your eyes fell shut as you slowly came off yet another high. You were sore as hell between your legs, and your thighs rubbed together as you felt cum smear and dribble down to your knees.

“So, that mean you guys are done, already? That wasn’t so bad,” you sighed with false bravado as you rolled back into Papyrus’s chest, flopping over with a squawk as his presence suddenly disappeared. Your breath caught in your throat as Papyrus grabbed your wrists tightly as he straddled you. It was only when you looked down that you realized that, unlike you and Sans, he never came.

“Not even close, Sweetheart,” Papyrus purred as he laced his fingers in yours and slammed them down into the mattress on either side of your head. “After all, why finish now when we’ve got all weekend?”

“Oh, fuck.”

Papyrus winked at you. “You’ve got the idea, Kitten. Now, let’s make ourselves some babies.”


End file.
